In recent years, a heat accumulating-type burner is employed in an industrial combustion furnace in order to enhance fuel economy. The heat accumulating-type burner is, as is shown in Patent Document 1 and Patent Document 2, a burner including a heat-accumulating element on an air supply/discharge path of the burner. The burner repeats combustion and exhausts alternately every relatively short period of time of about 30 seconds. In this operation, the heat held by the combustion gas is collected by a heat-accumulating element of the burner under the exhaust condition, whereas the combustion air is passed through the heat-accumulating element of the burner under the combustion condition to preheat the combustion air, so that high thermal efficiency is achieved.
In this heat accumulating-type burner, as shown in FIG. 4 for example, a burner portion 51 and a heat-accumulating portion 52 are connected to each other in series. The reference numeral 53 denotes a furnace wall; 54 a burner tile made of fireproof material; 55 a fuel nozzle; 56 a burner heat insulating wall made of fireproof heat insulating material; and 57 a heat accumulating element made of fireproof material. In this structured heat accumulating-type burner, the burner portion 51 and the heat-accumulating portion 52 are separated from each other. Thus, the thermal stress generated in the heat-accumulating portion 52 resulted from the thermal variation caused by the repeated combustion and air discharge is never applied to the burner portion 51. Therefore, the burner is excellent in durability. However, since most of the burner portion 51 and the whole heat accumulating portion 52 are installed outside the furnace, in order to prevent the heat release from these portions installed outside the furnace, it is required to provide a lining on the burner heat insulating wall 56 made of heat insulating material. Further, the higher the temperature at which the burner is intended to operate at will also prevent sintering fine ceramics from being used (for example, the temperature inside the furnace is 1400° C. or higher), therefore, the fireproof heat insulating wall 56 will be required to have a larger than desired thickness. In this case, there is a problem that the heat accumulating-type burner as a whole becomes large in size.
To solve this problem, there has been suggested a heat accumulating-type burner including a burner portion and a heat accumulating portion integral into one piece unit, as shown in FIG. 5. In FIG. 5, the reference numeral 61 denotes a fuel nozzle; 62 burner tile made of fireproof material; 63 a heat accumulating element made of fireproof material; 64 a burner heat insulating wall made of fireproof heat insulating material; and 65 a furnace wall. Since half or more portions of the burner portion of the heat accumulating-type burner shown in FIG. 5 are installed inside the furnace wall 65, there is an advantage that the portions installed outside the furnace can be reduced in terms of capacities. This heat accumulating-type burner has a structure in which the portion of the heat accumulating element 63 whose temperature will rise to high is located inside the furnace, whereas only the air supply/discharge port side of the heat accumulating element 63 whose temperature is low is located outside the furnace. Due to this structure, the burner heat-insulating wall 64 may be small in thickness, and as a result, the heat accumulating-type burner as a whole can be compact in size. However, in the heat accumulating-type burner shown in FIG. 5, since the burner tile 62 is located adjacent to the heat accumulating element 63, the thermal stress 66 generated in the heat accumulating element 63 resulted from the thermal variation caused by the repeated combustion and air discharge is applied to the burner tile 64. As a result, the burner tile 64 is cracked and damaged, or the burner tile 64 is pushed out to fall into the furnace. Thus, there is a problem in durability.
In such circumstances, there has been a demand for developing a heat accumulating-type burner compact in size but having durability.    [Patent Document 1] Japanese Patent Publication 1976-47131    [Patent Document 2] Japanese Laid-Open Utility Model Publication 1991-46742